Multi-chip package for LED chip and multi-chip package LED device including the multi-chip package

ABSTRACT

Provided is a multi-chip package light emitting diode (LED) device including a plurality of LED chips within a single package. The LED device may include a base substrate, a multi-chip package for a LED on the base substrate, and a light radiator surrounding the multi-chip package and radiating light emitted by the multi-chip package for a LED, wherein the multi-chip package for a LED may include a plurality of LED chips on a single wafer substrate.

PRIORITY STATEMENT

This application claims priority under U.S.C. §119 to Korean PatentApplication No. 10-2008-0060226, filed on Jun. 25, 2008, in the KoreanIntellectual Property Office (KIPO), the entire contents of which areincorporated herein by reference.

BACKGROUND

1. Field

Example embodiments relate to a multi-chip package for a light-emittingdiode (LED) and a LED device including the multi-chip package, and moreparticularly, to a LED multi-chip package in which a plurality of LEDchips may be disposed within a single package, and a LED deviceincluding the multi-chip package.

2. Description of the Related Art

Light-emitting diodes (LED) have undergone significant developmentssince the early 1990s using nitride semiconductor thin-films, and mostshort wavelength LEDs now use nitride semiconductor thin-films.Specifically, developments in semiconductor growth technologies anddevice fabricating technologies have improved efficiency of LEDs usingthe nitride semiconductor thin-films. As a result, nitride-basedsemiconductor LEDs may be applied to various fields, e.g., light sourcesof display devices, optical communications, or illuminations. Recently,a nitride-based semiconductor LED having an efficiency of about 120 lm/Wor higher has been developed. Such nitride-based semiconductor LEDs havesufficient efficiency to replace conventional light sources, e.g.,lamps.

Recently, due to the above-described developments in LEDs, light sourcesusing LEDs are being developed for home lighting, decorative lighting,or display lighting. LEDs, energy-conserving and environmentallyconscious light sources, are regarded as next-generation light sourcesfor lighting. Thus, LEDs are being developed to replace conventionallight sources. To use LEDs for lighting, LEDs are required to emit lighthaving the same brightness as conventional light sources. Thus, researchis being devoted to improving efficiency of LEDs simultaneously withapplying high power to LEDs such that the LEDs emit bright light.Currently, higher power and higher brightness LEDs are being developedwith a goal of obtaining light of about 1,000 lumens per LED chip.

However, a problem of such an approach may be applying increased powerto a single chip of a LED device for lighting. When relatively highpower is applied to a single LED chip, overall light brightnessincreases. However, light emitting efficiency decreases and heatcorresponding to the efficiency loss is generated. Thus, applyingincreased power to a single LED chip is regarded as a cause of eitherdecreasing the lifespan of the LED chip or diminishing reliability ofthe LED chip.

Furthermore, to control the generated heat, a cooling fan and a heatsink are required to be included in a LED device for lighting. Thus, themanufacturing costs and the volume of a LED device for lightingincrease. Furthermore, LED devices for lighting currently in use arerelatively small, and thus, are basically point light sources. Thischaracteristic may not satisfy the requirements for surface lightemission.

Generally, the brightness of light emitted by a LED device depends onthe amount of power applied to the LED device. Specifically, the drivingvoltage of a LED device may be between about 3.0 V and about 3.5 Vregardless of the size of the LED device. Thus, the brightness of lightemitted by the LED device varies according to the electric currentapplied to the LED device. For example, the brightness of light emittedby the LED increases in proportion to the magnitude of electricalcurrent applied to the LED. However, light emitting efficiency of theLED device may be at its peak when the electric current applied to theLED device is between about 5 mA and about 10 mA, and decreases as theelectric current applied to the LED device increases.

In most cases, an electrical current of about 350 mA or more may beapplied to high power and high brightness LEDs currently in use forincreasing brightness. As a result, light emitting efficiency may berelatively low. Furthermore, part of the applied electric currentcorresponding to decrease of the light emitting efficiency may beconverted to heat, and thus the temperature of a LED chip increases.Therefore, as described above, heat dissipating measures for dissipatingheat generated by a LED chip to the outside may be required forconventional LED devices, e.g. heat sinks.

To obtain a LED device with lower heat generation and higher lightemitting efficiency, driving a LED device by applying an electricalcurrent corresponding to the maximum light emitting efficiency may berequired. However, the brightness of light emitted by the LED maydecrease.

SUMMARY

Example embodiments provide a multi-chip package for a light-emittingdiode (LED), the multi-chip package having improved light emittingefficiency and generating less heat as compared to conventional LEDs,and a LED device including the multi-chip package. Example embodimentsalso provide a LED device having a simpler structure as compared toconventional LED devices.

According to example embodiments, a multi-chip package for a lightemitting diode (LED) may include a plurality of LED chips on a singlewafer substrate.

Each of the LED chips may include the wafer substrate; a first cladlayer on the wafer substrate; an active layer partially formed on topsurface of the first clad layer; a second clad layer on the activelayer; a first electrode partially formed on top surface of the firstclad layer; and a second electrode on the second clad layer. Accordingto example embodiments, the plurality of LED chips may share the singlewafer substrate and the single first clad layer. Furthermore, themulti-chip package may include a package block including the pluralityof LED chips; first and second bonding pads on the package block andconnected to an external power source; a first wiring pattern connectingthe first bonding pad and the first electrode of each of the LED chips;and a second wiring pattern connecting the second bonding pad and thesecond electrode of each of the LED chips. The first and second wiringpatterns may be on the wafer substrate.

Furthermore, the multi-chip package may include at least two wiringgroups each of which may include first and second bonding pads and firstand second wiring patterns. In example embodiments, each of the two ormore wiring groups may be connected to different LED chips.

According to example embodiments, a light emitting diode (LED) devicemay include a base substrate; a multi-chip package for a LED on the basesubstrate; and a light emitter surrounding the multi-chip package andemitting light generated in the multi-chip package for a LED, whereinthe multi-chip package for a LED may include a plurality of LED chips ona single wafer substrate.

According to example embodiments, some or all of the plurality of LEDchips may be turned on or off simultaneously. According to exampleembodiments, current density of electric current supplied to each of theLED chips may be between about 0.1 A/cm² and about 50 A/cm².

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingdetailed description taken in conjunction with the accompanyingdrawings. FIGS. 1-5 represent non-limiting, example embodiments asdescribed herein.

FIG. 1 is a sectional view of an example of a chip array structure of amulti-chip packaged LED device according to example embodiments;

FIGS. 2A-2C is a diagram roughly showing the inside of a multi-chippackage, in which a plurality of LEDs are disposed in a package block,for a LED, according to example embodiments; and

FIG. 3 is a sectional view roughly showing the overall structure of aLED device employing multi-chip packages according to exampleembodiments.

It should be noted that these Figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings are not, however, to scale and may notprecisely reflect the precise structural or performance characteristicsof any given embodiment, and should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments. For example, the relative thicknesses and positioning ofmolecules, layers, regions and/or structural elements may be reduced orexaggerated for clarity. The use of similar or identical referencenumbers in the various drawings is intended to indicate the presence ofa similar or identical element or feature.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

Hereinafter, a configuration and operations of a multi-chip package fora light emitting diode (LED) and a LED device using the multi-chippackage according to example embodiments will be described in detail byexplaining example embodiments with reference to the attached drawings.Example embodiments may, however, be embodied in different forms andshould not be construed as limited to example embodiments set forthherein. Rather, example embodiments are provided so that this disclosurewill be thorough and complete, and will fully convey the scope ofexample embodiments to those skilled in the art. In the drawings, thethickness of layers and regions are exaggerated for clarity. Likenumbers refer to like elements throughout the specification.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Like numbers indicate like elementsthroughout. As used herein the term “and/or” includes any and allcombinations of one or more of the associated listed items.

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of example embodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofexample embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, such as those defined incommonly-used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

Example embodiments suggest a multi-packaging method in which aplurality of LED chips may be disposed within a single package.Conventionally, a method of manufacturing a single LED device mayinclude forming a plurality of LED chips on a semiconductor wafer,dicing the wafer, packaging the LED chips, and combining the LED chippackages with other parts, e.g., heat sinks or lenses. In theconventional art, when LED chips are being packaged, either only asingle individually diced LED chip is packaged or a plurality ofindividually diced LED chips are packaged together. In contrast, exampleembodiments suggest a method of forming a group of a plurality of LEDchips electrically connected to each other while processing asemiconductor wafer and packaging the whole group.

FIG. 1 is a sectional view of an example of a chip array structure of amulti-chip packaged LED device according to example embodiments.Referring to FIG. 1, a plurality of LED chips 20 a, 20 b, and 20 c maybe formed on a single wafer substrate 11. According to the method ofmulti-chip packaging, the plurality of LED chips 20 a, 20 b, and 20 cformed on the single wafer substrate 11 may be packaged together.

Referring to FIG. 1, the structure of the LED chips 20 a, 20 b, and 20 cwill now be described in further detail. Each of the LED chips 20 a, 20b, and 20 c may include the wafer substrate 11 and a first clad layer 12formed on the wafer substrate 11. The LED chips 20 a, 20 b, and 20 c mayrespectively include active layers 13 a, 13 b, and 13 c partially formedon the top surface of the first clad layer 12, second clad layers 14 a,14 b, and 14 c formed on the active layers 13 a, 13 b, and 13 c, firstelectrodes 16 a, 16 b, and 16 c partially formed on the top surface ofthe first clad layer 12, and second electrodes 15 a, 15 b, and 15 cpartially formed on the second clad layers 14 a, 14 b, and 14 c. Theplurality of LED chips 20 a, 20 b, and 20 c may share the wafersubstrate 11 and the first clad layer 12. Although three LED chips 20 a,20 b, and 20 c are illustrated in FIG. 2, example embodiments are notlimited thereto, and the number of LED chips may vary if required.

As in other LED chips, the wafer substrate 11 may be formed of aninsulator, e.g., glass, silicon dioxide (SiO₂), quartz, sapphire(Al₂O₃), or AlN, a conductor, e.g., ITO or metals, or a semiconductor,e.g., silicon (Si). Furthermore, the first clad layer 12 may be ann-type semiconductor layer, and the second clad layers 14 a, 14 b, and14 c may be p-type semiconductor layers. In example embodiments, thefirst electrodes 16 a, 16 b, and 16 c on top of the first clad layer 12may be n-type electrodes, whereas the second electrodes 15 a, 15 b, and15 c may be p-type electrodes. Furthermore, the active layers 13 a, 13b, and 13 c may be formed of a compound semiconductor, e.g., a GroupII-VI oxide, for example, ZnO, MaO, CdO, or MnO, a Group II-VI nitride,for example, GaN, AlN, or InN, or a Group III-V compound, for example,InP, GaAs, or InAs.

Furthermore, if the LED device is a top emission type LED device, thesecond electrodes 15 a, 15 b, and 15 c may be transparent electrodes,and a reflecting panel (not shown) may be disposed on the wafersubstrate 11. In contrast, if the LED device is a bottom emission typeLED device, the second electrodes 15 a, 15 b, and 15 c may be reflectingelectrodes, and the wafer substrate 11 may be a transparent substrate.

Referring to FIGS. 2A-2C, example embodiments provide a singlemulti-chip package in which a plurality of LEDs are arranged. FIGS. 2Aand 2B respectively show examples of multi-chip packages 40 and 40′,which are fabricated by packaging four LED chips 20 (the multi-chippackage 40) and nine LED chips 20 (the multi-chip package 40′),respectively. In FIGS. 2A and 2B, the four LED chips 20 and the nine LEDchips 20 respectively share wafer substrates and first clad layers, asillustrated in FIG. 1.

For example, the plurality of LED chips 20 may be disposed inside apackage block 41. Each of the plurality of LED chips 20 may be connectedto first and second bonding pads 42 and 43, which are connected to anexternal power source and may supply electric current to the LED chips20, in parallel. For example, the first bonding pad 42 may be connectedto a first electrode (refer to FIG. 1) of each of the LED chips 20 via afirst wiring pattern 44. Furthermore, the second bonding pad 43 may beconnected to a second electrode (refer to FIG. 1) of each of the LEDchips 20 via a second wiring pattern 45. The first and second bondingpads 42 and 43 may be formed on the wafer substrate together with theLED chips 20 while processing a wafer.

In the structure of example embodiments, the current density of electriccurrent supplied to each of the LED chips 20 may be maintained betweenabout 0.1 A/cm² and about 50 A/cm². Thus, each of the LED chips 20 maybe driven with maximum efficiency. In example embodiments, although thebrightness of light emitted from each of the LED chips 20 is relativelysmall, the sum of the brightness of light emitted by the LED chips 20may be sufficient to be used for lighting due to the combination of theplurality of LED chips 20. Therefore, if the same electric current issupplied as in a conventional high power and high brightness LED device,the multi-chip package LED device according to example embodiments maybecome brighter due to the improved efficiency. Furthermore, themulti-chip package LED device according to example embodiments mayconsume less power to obtain the same brightness as light from aconventional high power and high brightness LED due to the improvedefficiency. Thus, the heat problem described above may not occur due tothe improved efficiency.

Furthermore, the multi-chip package LED device according to exampleembodiments may prevent or reduce diffusion of electric current, thediffusion occurring in conventional high brightness LED chips. In thecase of a conventional high brightness LED chip, the LED chip has a verylarge chip surface area to increase the brightness of light. Thus,uniformly diffusing electric current throughout the entire chip may bedifficult. In contrast, the multi-chip package LED device according toexample embodiments may use a plurality of LED chips each of which has asmaller chip surface area. Thus, the diffusion problem may not occur inthe multi-chip package LED according to example embodiments.Furthermore, in the multi-chip package LED according to exampleembodiments, each of the LED chips may not be individually packaged,rather, the plurality of chips may be packaged. Thus, the cost ofmanufacturing LED devices may be reduced. Furthermore, according toexample embodiments, even if some of the LED chips malfunction and donot emit light, the effect on the overall brightness of the multi-chippackage LED may be relatively low. Therefore, the lifespan of a lightsource manufactured by using the multi-chip packaging method may belonger than conventional light.

FIGS. 2A and 2B show that all the LED chips 20 disposed in the singlemulti-chip packages 40 and 40′ are simultaneously turned on or off.However, according to example embodiments, a multi-chip package may beconfigured such that some of the LED chips in a single multi-chippackage may be independently turned on or off. For example, at least twowiring groups, each of which includes at least one each of first andsecond bonding pads and at least one each of first and second wiringpatterns, may be disposed in a single multi-chip package, and each ofthe two or more wiring groups may be connected to different LED chips.

For example, a multi-chip package 40″ illustrated in FIG. 2C may includetwo first bonding pads 42 a and 42 b, two second bonding pads 43 a and43 b, two first wiring patterns 44 a and 44 b, and two second wiringpatterns 45 a and 45 b. Among them, the first bonding pad 42 a, thesecond bonding pad 43 a, the first wiring pattern 44 a, and the secondwiring pattern 45 a of a first wiring group may be electricallyconnected to LED chips 20′ of a first group.

Furthermore, the first bonding pad 42 b, the second bonding pad 43 b,the first wiring pattern 44 b, and the second wiring pattern 45 b of asecond wiring group may be electrically connected to LED chips 20″ of asecond group. In this structure of example embodiments, the LED chips20′ of the first group may be turned on if electric current is suppliedto the first wiring group, and the LED chips 20″ of the second group maybe turned on if electric current is supplied to the second wiring group.Although two wiring groups are illustrated in FIG. 2C as an example,three or more wiring groups may be prepared according to the design of amulti-chip package.

FIG. 3 is a sectional view roughly showing the overall structure of aLED device 50 employing multi-chip packages 40, 40′, and 40″, accordingto example embodiments. Referring to FIG. 3, the LED device 50 accordingto example embodiments may include a base substrate 51, the multi-chippackage 40, 40′, or 40″ for an LED diode which is disposed on the basesubstrate 51, and a light emitter 56 which surrounds the multi-chippackage 40, 40′, or 40″ and may be for emitting light generated in themulti-chip package 40, 40′, or 40″ to the outside. Furthermore, leads 52and 53, which are connected to an external power source and are forsupporting the LED device 50, may be disposed on the base substrate 51of the LED device 50. The leads 52 and 53 may be electrically connectedto bonding pads (refer to FIGS. 2A through 2C) of the multi-chip package40, 40′, or 40″ via wires 54 and 55. The light emitter 56 may be a lensformed of transparent glass or polymer, for example. Various forms ofthe light emitter 56 may be well known in the art.

As described above, the LED device 50 according to example embodimentsmay have improved light emitting efficiency, and thus, problems, e.g.,heat generation, seldom occur. Therefore, the LED device 50 may have asimplified structure as illustrated in FIG. 3, because the LED device 50does not require a heat dissipating structure, for example, a heat sink.Furthermore, a plurality of LED chips may be disposed inside themulti-chip packages 40, 40′, and 40″ according to example embodiments,and thus, overall surface areas of the multi-chip packages 40, 40′, and40″ may increase. Thus, the LED device 50 employing the multi-chippackages 40, 40′, and 40″ may have more of a surface light emissioncharacteristic than a point light emission characteristic, unlikeconventional LED devices.

While example embodiments have been particularly shown and describedwith reference to example embodiments thereof, it will be understood bythose of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the following claims.

1. A multi-chip package for a light emitting diode (LED) comprising aplurality of LED chips on a single wafer substrate.
 2. The multi-chippackage of claim 1, wherein each of the LED chips comprises: the wafersubstrate; a first clad layer on the wafer substrate; an active layerpartially formed on top surface of the first clad layer; a second cladlayer on the active layer; a first electrode partially formed on topsurface of the first clad layer; and a second electrode on the secondclad layer.
 3. The multi-chip package of claim 2, wherein the pluralityof LED chips share the single wafer substrate and the first clad layer.4. The multi-chip package of claim 2, further comprising: a packageblock including the plurality of LED chips; first and second bondingpads on the package block and connected to an external power source; afirst wiring pattern connecting the first bonding pad and the firstelectrode of each of the LED chips; and a second wiring patternconnecting the second bonding pad and the second electrode of each ofthe LED chips.
 5. The multi-chip package of claim 4, wherein the firstand second wiring patterns are on the wafer substrate.
 6. The multi-chippackage of claim 4, further comprising: at least two wiring groups eachincluding the first and second bonding pads and the first and secondwiring patterns.
 7. The multi-chip package of claim 6, wherein each ofthe two or more wiring groups is connected to different LED chips.
 8. Alight emitting diode (LED) device comprising: a base substrate; amulti-chip package for a LED on the base substrate; and a light emittersurrounding the multi-chip package and emitting light generated in themulti-chip package for a LED, wherein the multi-chip package for a LEDincludes a plurality of LED chips on a single wafer substrate.
 9. TheLED device of claim 8, wherein each of the LED chips comprises: thewafer substrate; a first clad layer on the wafer substrate; an activelayer partially formed on top surface of the first clad layer; a secondclad layer on the active layer; a first electrode partially formed ontop surface of the first clad layer; and a second electrode on thesecond clad layer.
 10. The LED device of claim 9, wherein the pluralityof LED chips share the single wafer substrate and the first clad layer.11. The LED device of claim 9, wherein the multi-chip package for a LEDcomprises: a package block including the plurality of LED chips; firstand second bonding pads on the package block and connected to anexternal power source; a first wiring pattern connecting the firstbonding pad and the first electrode of each of the LED chips; and asecond wiring pattern connecting the second bonding pad and the secondelectrode of each of the LED chips.
 12. The LED device of claim 11,wherein the first and second wiring patterns are on the wafer substrate.13. The LED device of claim 11, wherein the plurality of LED chips areturned on or off simultaneously.
 14. The LED device of claim 11, whereinthe multi-chip package comprises at least two wiring groups eachincluding the first and second bonding pads and the first and secondwiring patterns.
 15. The LED device of claim 14, wherein each of the twoor more wiring groups is connected to different LED chips.
 16. The LEDdevice of claim 15, wherein some of the plurality of LED chips areturned on or off independently.
 17. The LED device of claim 8, whereincurrent density of electric current supplied to each of the LED chips isbetween about 0.1 A/cm² and about 50 A/cm².